An LED circuit capable of dividing a current into two or more channels of equal or unequal proportions provides certain advantages. For example, multiple LED channels of different colors may share a single channel LED driver in a correlated color temperature (CCT) tuning system without the need for multi-channel DC/DC converters.
In general, there are two approaches to current division. The first method is the time-division method. In the time division method, each channel conducts the full amplitude of the input current within the allocated time slot. The second method is dividing the current by amplitude. The second method operates in the analog domain and creates multiple currents of small amplitudes, the sum of which is equal to that of the input current. Dividing a current by amplitude provides certain advantages, including but not limited to, avoiding switching noise and maximizing the utilization of LEDs, thereby increasing the efficacy.
In general, analog current division in LEDs achieved though parallel LED arrays. Resistors are connected in series on each array in order to linearize the forward voltage. Parallel LED arrays are best driven with equal current so as to avoid current hogging. Therefore the current must be divided into equal proportions and the system can only deal with a very limited amount of mismatch between the parallel LED arrays.
It would be beneficial to provide an LED circuit capable of dividing a current into two or more channels via parallel LED arrays in which the current is divided into arbitrary rations and can deal with a large mismatch between the parallel LED arrays.